The blood-brain barrier (BBB) is crucial for complex issues such as drug delivery, pathogenesis of chronic neurological diseases involving BBB dysfunction (e.g., brain tumors, ischemia, hypoxia, brain edema, multiple sclerosis, and meningitis) and issues related to bio-defense. Since the BBB selectively (by specific transport mechanisms) excludes most blood-borne substances and xenobiotics from entering the brain, protecting it from systemic influences. Unfortunately, bio-defense systems that developed to protect the brain from potentially dangerous substances may also contribute to the phenomenon known as multiple drug resistance (MDR) during treatment of several CNS disorders, such as drug refractory epilepsy or intractable brain tumors. Every year millions of dollars are spent by pharmaceutical companies to develop alternative pharmaceutical strategies that bypass the shielding of brain parenchyma and to study new therapeutic approaches using in vivo or in vitro models of the BBB, many of which end up not working. Rationale CNS drug design cannot entirely and exclusively rely upon the physical-chemical properties of putative neurotherapeutics, since lipophilicity alone is a poor predictor for drug penetration into the CNS. This is particularly true for 3 large families of CNS drugs, antineoplastics, antivirals and antiepileptics. Studies performed in small animals including rodents cannot be directly extrapolated to human tissue. Preliminary results from this and other laboratories have convincingly demonstrated that use of rodent brain endothelial cells and in general endothelial cell lines from non human sources as models of clinical pharmacology are flawed. We propose to: 1) To study the effects of multiple drug resistance expression in endothelial-glial co-culture grown under dynamic conditions and to compare permeability values obtained in a comparable BBB model based on Transwell-type technology. 2) To validate the current design of the cartridge and implement improvements to the existing DIV-BBB to address current deign problems. 3) To validate the design of the electronic measurement system. The improvement in the current TEER design is the ability to measure the impedance of BBB at various frequencies. We propose to develop and validate an improved dynamic in vitro blood-brain barrier (DIV-BBB) model that reproduces the functional characteristics of the BBB in vivo, features higher predictability, and is fully scalable and customizable. As such, it will be perfectly suited for extensive pharmacological and physiological studies and will accelerate the process leading to new and more effective drug therapies aimed at CNS diseases. [unreadable] [unreadable] [unreadable]